1. Field of the Invention
The present invention relates to an information record disc, such as an optical disc, which is used to record information, and more particularly relates to an information record disc, which has a wobbled record track and on which information can be additionally written and re-written. Moreover, the present invention relates to an information recording apparatus for recording information onto such an information record disc.
2. Description of the Related Art
A CD (Compact Disk) on which information can be recorded or written just once is typically known as a CD-R (CD-Recordable). Also, a CD on which information can be re-written a plurality of times is typically known as a CD-RW (CD-ReWritable). Record tracks of the CD-R and the CD-RW are slightly meandering or wobbling in a radius direction. This meandering condition of the record track is typically referred to as a xe2x80x9cwobblingxe2x80x9d or xe2x80x9cwobblexe2x80x9d.
On the other hand, in order to record information onto a disc or reproduce the information recorded on the disc, there is required the information for indicating an absolute address (or an absolute time) on the disc. Hereafter, this information is referred to as xe2x80x9cpre-informationxe2x80x9d.
In case of the CD-R and the CD-RW, the pre-information is recorded on the disc by FM-modulating the wobble. Actually, a carrier signal used to form the wobble is FM-modulated in accordance with the pre-information. The wobble corresponding to a wave form of this FM-modulated carrier signal is formed on the record track. Accordingly, the pre-information is recorded on the disc.
When recording the information onto the CD-R or the CD-RW or when reproducing the information recorded on the CD-R or the CD-RW, a recording apparatus or a reproducing apparatus reads in the wobble formed on the CD-R or the CD-RW, and controls a rotation number of the CD-R or the CD-RW or generates a record track, in accordance with the information obtained from the wobble. For this reason, it is not desirable that the frequency of the wobble is widely changed. Thus, an amount is very slight which is allowable for the change in the frequency of the wobble, in order to superimpose the pre-information onto the wobble. For example, if the frequency of the wobble is 22.05 kHz, the amount is only xc2x11 kHz which is allowable for the change in the frequency of the wobble in order to superimpose the pre-information. Consequently, it is not easy for the recording apparatus or the reproducing apparatus to accurately detect the pre-information from the wobble. This results in a problem that the accuracy to specify a position on the disc is poor.
If the accuracy to specify the position on the disc is poor, a record position may be easily deviated when linking the new record information with the record information already recorded on the disc. Consequently, for example, there may be a case that the new record information is overwritten onto the already recorded information or that a gap which cannot be estimated is induced between the already recorded information and the new record information. In order to avoid such a case, in the CD-R and the CD-RW, a buffer region is reserved by recording dummy data following the record information when the operation for writing the record information is ended. However, this has a defect that the buffer region brings about a loss of a memory capacity of the disc.
On the other hand, a recordable DVD, such as a DVD-RAM and the like, uses a method different from those of the CD-R and the CD-RW to record the pre-information on the disc. That is, the recordable DVD employs a method of forming a pre-pit (embossed pit) on the disc to thereby record the pre-information on the disc.
However, this method has the configuration in which the pre-pit is formed only on the recordable DVD, which results in a largely structural difference between a disc dedicated to a reproduction and a recordable disc. Thus, it is difficult to attain a compatibility between both of them. For example, this brings about a problem that it is difficult for a common reproduction unit to reproduce the information recorded on the recordable disc having the pre-pit and also reproduce the information recorded on the disc which is dedicated to the reproduction and does not have the pre-pit.
The present invention is proposed in view of the above mentioned problems. It is therefore an object of the present invention to provide an information record disc, which can easily attain a compatibility between a record disc dedicated to a reproduction and a recordable record disc and also which can allow to detect a record position of record information on a disc easily and accurately, as well as an information recording apparatus, which can detect a record position of record information on a disc easily and accurately.
The above object of the present invention can be achieved by an information record disc provided with: a track formed on a disc surface, on which record information to be reproduced is recorded or to be recorded; and a wobble formed on the track such that a phase of the wobble is changed at a plurality of locations on the track and that positional information indicative of a position on the disc surface is recorded as a change in the phase of the wobble. The record information is arranged at a predetermined arrangement cycle, and includes a synchronization signal to attain a synchronization when the record information is recorded or reproduced. An interval at which the phase of the wobble is changed on the track is equal to N times (N is an integer equal to or greater than 1) of the predetermined arrangement cycle of the synchronization signal when the record information is recorded on the track.
According to the information record disc of the present invention, when the record information is recorded on the track, the interval at which the phase of the wobble is changed is equal to N times of the predetermined arrangement cycle of the synchronization signal. This implies that a certain positional relationship exists between the position at which the phase of the wobble is changed and the position at which the synchronization signal in the record information is placed. Thus, on the basis of such a certain positional relationship, just by detecting the change of the phase of the wobble, the position at which the synchronization signal is recorded or the position at which the synchronization signal is to be recorded can be specified or identified easily. Therefore, it is possible to easily specify or identify the position at which the record information is to be recorded on the disc.
Further, since the positional information indicative of the position of the disc surface is recorded as the change of the phase of the wobble, it is possible to record the positional information clearly while maintaining the frequency of the wobble constant. Therefore, while satisfying such a demand that the information obtained from the wobble is used for the rotation control of the disc and the generation of the record clock, it is possible to improve the detection accuracy of the positional information. Further, it is possible to accurately detect the change of the phase of the wobble, and thereby accurately detect the record position of the record information on the disc.
As detailed above, according to the information record disc of the present invention, it is possible to specify the record position of the information on the information record disc easily and accurately. Thus, it is possible to prevent the new record information from being overwritten to the already recorded information, without reserving the buffer region by using the dummy data and the like. Thus, it is possible to exclude the unnecessary usage of the memory region on the information record disc, and also possible to substantially increase the memory capacity of the information record disc.
In addition to such effects, according to the information record disc of the present invention, it is possible to easily attain the compatibility between the information record disc dedicated to the reproduction and the recordable information record disc. Accordingly, the reproduction of the information recorded on the information record disc can be attained by using the common reproducing apparatus without considering the difference between the information record disc dedicated to the reproduction and the recordable information record disc. This attainment contributes to the simplification and the cost reduction in the structure of the reproducing apparatus.
In one aspect of the information record disc of the present invention, the synchronization signal in the record information is placed at a position at which the phase of the wobble is changed when the record information is recorded on the track.
According to this aspect, it is possible to specify the position at which the synchronization signal is recorded or to be recorded, just by detecting the change of the phase of the wobble. Thus, it is possible to easily specify the position at which he record information is to be recorded on the disc. Incidentally, in case that N=1, the synchronization signal is always placed at a position at which the phase of the wobble is changed, and the phase of the wobble is always changed at the position where the synchronization signal is placed. On the other hand, in case that N is not less than 2, the synchronization signal is always placed at the position where the phase of the wobble is changed, but the phase of the wobble is not always changed at the position where the synchronization signal is placed.
In another aspect of the information record disc of the present invention, the change of the phase of the wobble is an inversion of the phase.
According to this aspect, by recording the positional information as the inversion of the phase of the wobble, the detection of the positional information can be easily performed. Even if the noise is induced in the detection of the positional information, it is still possible to accurately detect the positional information.
Further, rather than to detect a subtle change in the frequency of the wobble, it is easier to detect the inversion of the phase of the wobble, it is possible to improve the detection accuracy of the positional information by recording the positional information as the inversion of the wobble, as compared with the detection accuracy of the pre-information in the conventional CD-R or CD-RW.
In this aspect, the positional information may be two-values data of an RLL (Run Length Limited) code in which a longest inversion interval is limited.
By constituting in this manner, it is possible to limit the interval of the inversion of the phase of the wobble. As a result, it is possible to avoid such an occasion that the inversion of the phase does not occur for a long period of time. Thus, it is possible to surely detect the inversion of the phase.
In another aspect of the information record disc of the present invention, a cycle of the wobble is equal to 4P times (P is an integer equal to or greater than 1) of a cycle of a standard clock, which is used as a standard to record the record information, and is also equal to 1/M (M is an integer equal to or greater than 2) of the predetermined arrangement cycle of the synchronization signal.
According to this aspect, in case of using the Costas loop method for the detection of the wobble, a first signal for wave-detection in phase to the wobble and a second signal for wave-detection, which is out of the phase by xc2xc cycle with respect to the first signal for wave-detection, may be used. Then, those first and second signals for wave-detection are generated from the standard clock used for the detection of the wobble. In this case, if the cycle of the wobble is set to 4P times of the cycle of the standard clock, it is possible to easily generate the second signal for wave-detection which is out of the phase by xc2xc cycle with respect to the first signal for wave-detection. In addition, the cycle of the wobble may be set to 1/M of the predetermined arrangement cycle of the synchronization signal, so that the correspondence between the wobble and the record information can be simplified.
The above object of the present invention can be also achieved by an information recording apparatus for recording record information to be reproduced onto the above described information record disc o the present invention (including various aspects thereof). The information recording apparatus is provided with: a wobble detecting device for detecting a wobble signal corresponding to the wobble from the information record disc; a phase detecting device for detecting a phase of the wobble signal and then generating a detection signal indicative of a change in the phase of the wobble signal; a positional information demodulating device for demodulating the positional information in accordance with the detection signal; a signal generating device for detecting a timing when the phase of the wobble signal is changed from the detection signal, and then generating a control signal indicative of the predetermined arrangement cycle of the synchronization signal in the record information on the basis of the detected timing; and a recording device for specifying a record position on the disc surface on the basis of the positional information demodulated by the positional information demodulating device and the control signal generated by the signal generating device, and then recording the record information from the specified record position so that the interval at which the phase of the wobble is changed is equal to N times the predetermined arrangement cycle of the synchronization signal.
According to the information recording apparatus of the present invention, the positional information indicating the position on the disc is recorded as the change in the phase of the wobble. The wobble detecting device detects the wobble signal corresponding to the wobble having such a phase change from the information record disc. In the detected wobble signal, the positional information is included as the change in the phase. Then, the phase detecting device detects the phase of the wobble signal, and generates the detection signal indicating the change in the phase of the wobble signal. Then, the positional information demodulating device demodulates the positional information on the basis of this detection signal. Further, the signal generating device detects the timing when the phase of the wobble is changed out of the detection signal, and generates the control signal indicating the predetermined arrangement cycle of the synchronization signal on the basis of this detected timing. Then, the recording device specifies the position on the disc on the basis of the positional information and the control information, and starts recording the record information from this specified position. At this time, the record information is recorded to have a certain positional relationship so that the interval at which the phase of the wobble is changed becomes N times of the predetermined arrangement cycle of the synchronization signal.
Accordingly, it is possible to easily and accurately specify the position at which the record information is to be recorded on the basis of the detection result of the change in the phase of the wobble, and thereby possible to accurately record the record information at this specified position.
In one aspect of the information recording apparatus of the present invention, the phase detecting device comprises an averaging device for averaging timings when the detected phases of the wobble signal are changed.
According to this aspect, it is possible to improve the accuracy of the timing at which the phase is changed. As a result, it is possible to improve the accuracy of the control signal generated by the signal generating device, so that it is possible to improve the accuracy of the record position of the record information.
The nature, utility, and further features of this invention will be more clearly apparent from the following detailed description with respect to preferred embodiments of the invention when read in conjunction with the accompanying drawings briefly described below.